IMMUNOREACTIVE HUMAN CHORIONIC-GONADOTROPIN BETA-CORE FRAGMENT IN HUMAN PITUITARY

The human pituitary has been shown to produce small amounts of immunoreactive human chorionic gonadotropin (hCG) and its alpha- and beta- subunit (hCG alpha, hCG beta). The aim of the present studies was to further examine the various hCG-related materials in the human pituitary, particularly to search for the existence of pituitary hCG beta core fragment (hCG beta cf) - like material. HCG beta cf has been found in the urine of pregnant women, patients with trophoblastic tumors and also in postmenopausal women. Gel chromatography of pituitary extract on Superdex 200 showed three distinct peaks of hCG-related immunoreactivities, i.e. hCG, hCG beta and hCG beta cf, which were distinguishable from hLH and hLH beta peaks. HCG beta cf was recognized by a specific immunometric assay (crossreactivities with hCG beta 0.016%, hLH beta 0.04%), but unreactive in an hLH + hLH beta assay. It was purified and displayed physical properties similar to those of hCG beta cf derived from pregnancy urine. Apart from immunological differences between the small molecular weight forms or fragments of hCG and LH origin, reversed phase HPLC was able to physically discriminate between hCG beta cf and hLH beta fragment. The latter was much more abundant than the former in the pituitary extract. HCG beta cf showed microheterogeneity related to its sialic acid content. In conclusion, the present data indicate that immunoreactive hCG beta cf is present in human pituitary extracts. The physical and immunological properties of pituitary hCG beta cf are distinguishable from those of the more abundant hLH beta and its fragment, and compare favorably with those of urinary hCG beta cf of trophoblastic origin.